Cathode support and contact arrangement

ABSTRACT

An electron discharge device of the planar disk electrode type employs an electrode with a peripheral groove and a support and contact arrangement for the electrode. A conductive cylinder surrounding the electrode has a groove in its inner surface and a garter spring is positioned between and engages the grooves in both the electrode and the cylinder so that the turns of the spring provide high electrical conductivity between the electrode and the cylinder while minimizing the thermal conductivity.

United States Patent Beggs 51 Apr. 25, 1972 [54] CATHODE SUPPORT AND CONTACT ARRANGEMENT [72] Inventor: James E. Beggs, Schenectady, NY.

[73] Assignee: General Electric Company [22] Filed: May 21, 1970 21 Appl. No.: 39,462

[52] U.S.Cl ..313/ll,3l3/42,313/47, 313/257, 313/268, 313/292 [51] Int. Cl. ..H01j 1/02 [58] Field ofSearch ..3l3/ll,3739,

[56] References Cited UNITED STATES PATENTS 2,825,832 3/1958 Cutler ..3l3/42 X 3,252,039 5/1966 Claypool ..313/257X Primary Examiner-Alfred L. Brody Attorney-Paul A. Frank, John F. Ahern, Julius J. Zaskalicky, Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Forman [5 7] ABSTRACT An electron discharge device of the planar disk electrode type employs an electrode with a peripheral groove and a support and contact arrangement for the electrode. A conductive cylinder surrounding the electrode has a groove in its inner surface and a garter spring is positioned between and engages the grooves in both the electrode and the cylinder so that the turns of the spring provide high electrical conductivity between the electrode and the cylinder while minimizing the thermal conductivity.

8 Claims, 4 Drawing Figures CATHODE SUPPORT AND CONTACT ARRANGEMENT My invention relates to electron discharge devices of the planar disk electrode type and in particular to an arrangement for supporting and contacting a disk electrode in such a device.

It is recognized that to obtain long life from a device employing a thermionic cathode, it is essential that only highly stable refractory materials be used for supporting the cathode. Conventionally, however, in attaching the cathode to the support, a solder alloy is employed. I have discovered that vapors liberated at high temperatures from those solder alloys can be harmful to the cathode emission and also may cause damaging deposits to form on insulation surfaces. Again, the more active metals required for a satisfactory solder alloy may chemically react with the oxides impregnating a thermionic cathode and shorten its operating life.

In my prior application, Ser. No. 810,951 filed Mar. 27, 1969 and assigned to the assignee of the present invention, now US. Pat. No. 3,564,318 there is discloseda corrugated metal ribbon which is attached between the outer circumference of a planar grid or cathode electrode and an interior opening of a contact member, the corrugated member accommodating thermal expansion differentials without distortion of the electrodes or contact members so that the electrodes can be mounted and maintained in precise spaced relationship. While such structure has excellent mechanical properties, it requires the use of welding or brazing procedures during fabrication. The solder, welding, or brazing materials employed in this manner later introduce sublimation problems during operation of the device and also cause reactions between such materials and the oxides impregnating the cathode.

It is the primary object of my invention to provide a new and improved support for the cathode electrode of an electron discharge device.

It is another object of my invention to provide a support for a disk-type electrode which obviates the need of solders.

It is still another object of my invention to provide a support for a disk-type electrode which provides low electrical resistance between the electrode and the support while minimizing thermal conductivity therebetween.

It is another object of my invention to provide a support for the electrodes in an electron discharge device which both facilitates the assembly and reduces the cost of assembling the device.

In accordance with my present invention, the planar disk electrode of an electron discharge device is provided with a peripheral groove and a conductive cylinder is positioned concentric with and spaced from the electrode so that a garter spring may be interposed between the groove in the electrode and the groove in the supporting cylinder to maintain the electrode in a mechanically stable position while providing both good electrical conductivity between the electrode and the cylinder and minimizing thermal conductivity between these two members. In this way, the support obviates the need for soldering, brazing, or welding, reducing to zero the sublimation of materials employed in such processes, which materials tend to reduce the life and efiiciency of the electron discharge device.

The features and advantages which characterize my invention will become more apparent as the following description proceeds, reference being taken to the accompanying drawings and its scope will be pointed out in the appended claims. In the drawings:

FIG. 1 is a sectional elevational view of an electron discharge device embodying my invention;

FIG. 2 is an exploded view of a cathode support structure in accordance with my invention;

FIG. 3 is an elevational cross-sectional view of the assembled support structure of FIG. 2; and

FIG. 4 is a cross-sectional elevational view of another type of an electron discharge device employing a modification of my invention.

The electron discharge device illustrated in FIG. 1 comprises an anode 1, a cathode 2 of the porous type, a control electrode or grid 3 bonded to the upper surface of cathode 2 and separated therefrom by an insulating layer 4, and a heater 5 attached to the lower surface of cathode 2. Three concentric cylinders support the electrodes in spaced relation. Thus, outer cylinder 6, which may comprise an insulating material such as a spinel, supports anode l and inner cylinder 7 supports the bonded cathode, control grid structure.

To efiect the latter support without requiring the use of solders or brazing materials, in accordance with my invention, cathode 2 is provided with a peripheral groove 8, cylinder 7, a groove 9 on its inner surface, and a resilient conductive member 10 is positioned between cylinder 7 and cathode 2 and engages both grooves 8 and 9. Resilient member 10 is formed of a suitable refractory metal such as tungsten which is helically wound to form a garter spring whose ends are hooked together to prevent separation.

In the device of FIG. 1, the unitary heater cathode control grid structure preferably is of the type described and claimed in my concurrently filed U.S. Pat. No. 3,599,031 assigned to the assignee of this present invention. Such a unitary heater cathode and control grid structure is formed by coating a disk of a porous refractory metal which forms cathode 2 with an inorganic insulating layer 4 such as, for example, boron nitride forming a grid pattern 3 on one side of the disk by an electrodeposition process and forming openings in the film and insulating layer corresponding to the pattern. The heater 5, which is illustrated as of the conventional metal-clad insulated type, is attached to the lower surface of cathode 2. In this structure, contact to control grid 3 is made by means of a plurality of resilient fingers 11 attached to the upper end of an intermediate conductive cylinder 12. The other end of cylinder 12 is attached to conductive disk 13 which provides an externally available contact to the control grid. Similarly, the lower ends of cylinder 7 and one terminal 14 of heater 5 are connected to a second conductive disk 15 which provides an externally available contact for the cathode and one terminal of the heater. A second terminal 16 for heater 5 is connected to a conductive disk 17 at the base of the discharge device.

The exploded view of FIG. 2 illustrates in better detail the groove 8 in cathode body 2 and groove 9 in a supporting cylinder 7. Likewise, this figure illustrates how the resilient conductive member or garter spring 10 is formed with the two ends l8, l9 hooked together to avoid the use of any solder or brazing material. The unitary heater, cathode, control grid structure shown in FIG. 2 differs from that of FIG. 1 in that it employs a heater 20 bonded to the bottom surface of cathode 2 and separated therefrom by an inorganic insulating layer 21. Details of the construction of this unitary electrode structure are described in my aforementioned US. Pat. No. 3,599,031. Leads 22, 23 to the heater 20 are formed of a refractory metal such as tungsten and include a resilient portion 24 in the form of a coiled turns of the conductor. Leads 22, 23 pass through openings 25, 26 in an insulating disk 27 and are provided with externally accessible terminals 28, 29.

FIG. 3 shows the cathode support structure of FIG. 2 in an assembled form. In assembling the structure of FIG. 3, garter spring 10 is snapped into position in groove 8 in disk 2, after which pressure is applied to the cathode body and the garter spring snaps into groove 9 in cylinder 7. In positioning the cathode in this fashion, the ends of the heater 20 engage the upper ends of conductors 22, 23 and in so doing compress the spring portions 24 of these conductors so that good contact between conductors 22, 23 and the heater is assured. If heater 20 is formed of a refractory metal such as tungsten and leads 22, 23 are formedof a similar material, when the assembled device is evacuated and baked out, the upper ends of leads 22, 23 sinter to the terminals of the heater 20 to from a low re sistance connection to the heater.

In the electron discharge device illustrated in FIG. 4, a modification of the unitary heater, cathode, control grid is employed. In this device, a layer of inorganic insulating material 4 covers both surfaces of cathode body 2, as well as its peripheral groove. The control grid 3 bonded to the upper surface of the cathode and the inorganic insulating layer 4 extends over the edges of insulation 4 to provide a grid contact region 30 which engages the turns of garter spring 10. In the device of FIG. 4, anode l is supported by an insulating cylinder 6 and the unitary heater, cathode, control grid structure is supported by conductive cylinder 31. Cylinder 31 has a groove at its upper end in the form of a shoulder 32 which receives garter spring 10. A third conductive cylinder 33 provides contact to the cathode by means of a plurality of pins 34 which extend angularly upward from the upper end of cylinder 33 into the body of cathode 2 to make resilient contact with the cathode. In other respects, the structure of the device of FIG. 4 is similar to that shown in FIG. 3. Heater leads 22, 23 pass through a ceramic insulator 35 formed of a suitable material such as forsterite which supports the leads. In assembling this structure, garter spring is placed in position in groove 4, then pressure is applied to the cathode to snap garter spring 10 into position in groove 9 on shoulder 32. In so doing, contact is made between the garter spring and grid contact region 30. The turns of the spring remain under tension between grooves 4 and 9, thus providing a secure mounting for the cathode over its full operation range.

An important feature of my improved cathode support and contact arrangement is that the garter spring provides a series of low resistance contacts between the support member and the cathode. It also provides sufficient thermal isolation to permit efficient operation of the cathode. As a consequence, an additional advantage of my invention is that it provides a support and contact which is mechanically simple, low in cost, and easy to assemble. An important feature is that in doing so, it obviates all dangers of sublimation of solder and welding materials, thus assuring longer life and improved operating characteristics for an electron discharge device employing my invention.

While I have shown and described several embodiments of my invention, it will be obvious to those skilled in the art that many changes and modifications may be made without departing from my invention in its broader aspects and I, therefore, intend the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In an electron discharge device of the planar disk type the improvement comprising:

a. a planar disk electrode including a cathode member and having a single recessed peripheral groove thereabout;

b. a conductive electrode support cylinder extending into said device concentrically with said planar electrode,

b,.) said support cylinder having an inboard end having therein a groove in its inner surface laterally surrounding said disk electrode,

c. a single resilient helical toroidal conductive member engaging both of said grooves to support said disk electrode resiliently and removably within the inboard end of said support cylinder only and in good electrical contact but poor thermal contact therewith.

2. In the device of claim 1, the improvement wherein said planar disk electrode further includes an insulating film on a first planar surface thereof and a control grid structure upon said insulating film.

3. The support of claim 1 in which said resilient conductive member comprises a garter spring comprising a resilient helically wound conductor.

4. In the device of claim 2, a control grid which extends over a portion of the side of the planar disk electrode structure and is insulated from said cathode, said helix being in electrical contact with said grid extension.

5. The device of claim 1 in which the peripheral groove is in 4 the cathode and said helix is in electrical contact with said cathode. I

6. The device of claim 4 which includes a second conduc- 

1. In an electron discharge device of the planar disk type the improvement comprising: a. a planar disk electrode including a cathode member and having a single recessed peripheral groove thereabout; b. a conductive electrode support cylinder extending into said device concentrically with said planar electrode, b1.) said support cylinder having an inboard end having therein a groove in its inner surface laterally surrounding said disk electrode, c. a single resilient helical toroidal conductive member engaging both of said grooves to support said disk electrode resiliently and removably within the inboard end of said support cylinder only and in good electrical contact but poor thermal contact therewith.
 2. In the device of claim 1, the improvement wherein said planar disk electrode further includes an insulating film on a first planar surface thereof and a control grid structure upon said insulating film.
 3. The support of claim 1 in which said resilient conductive member comprises a garter spring comprising a resilient helically wound conductor.
 4. In the device of claim 2, a control grid which extends over a portion of the side of the planar disk electrode structure and is insulated from said cathode, said helix being in electrical contact with said grid extension.
 5. The device of claim 1 in which the peripheral groove is in the cathode and said helix is in electrical contact with said cathode.
 6. The device of claim 4 which includes a second conductive cylinder surrounding said support cylinder and contact means connecting said second cylinder with said control grid.
 7. The device of claim 2 in which a heater is attached to a second surface of said cathode, said first cylinder is supported upon a base member and a pair of leads extend through said base member within said cylinder for contacting said heater.
 8. The device of claim 7 in which said leads include resilient portions to facilitate contacting said heater. 